2005 Chevy Truck AC/HEATER

Often times it is an overtravel(or false indication) of an actuator. The system then defaults to one extreme or the other, and it can create a difference side to side. The system sets codes when this happens, and you need a scan tool that will communicate with HVAC to access the codes. There are possibilities of a bad actuator, mechanical problem in the case(stuck/binding door), or software problems. What I would try first is removing the HVAC/ECAS fuse in the underhood fuse block for 60 seconds, and then reinstall. Turn the key on and don't touch the panel for about the same time. See if proper operation resumes. What this does is clears the codes, and recalibrates the actuator travel limits. It may function for a while, or may fault immediately. From there you would almost need a scan tool to isolate which actuator is causing the problem.